The present invention relates to a flat panel type lighting device utilizing a dielectric barrier type external electrode fluorescent lamp (hereinafter referred to as a “EEFL lamp”), and especially relates to a socket assembly for supplying electric power to a plurality of EEFL lamps.
A flat panel type lighting device utilizing EEFL lamp is widely used for a back light unit for a display unit requiring high brightness such as a liquid crystal display TV set.
In such conventional back light unit, a plurality of EEFL lamps is arranged in parallel. External electrodes at the both ends of each lamp are inserted into each of the plurality of capsule type sockets, which are arranged in a pair of power supply units. A high frequency voltage is applied between the pair of power supply units, which light each lamp by discharge (refer to Japanese Patent Application Laid-Open 2002-8408).
In such conventional back light unit, the external electrode portions of the both ends of EEFL lamp are inserted into a plurality of capsule type sockets arranged facing each other in a pair of power supply units. High level of manufacturing and assembling techniques are necessary for the power supply units, because from 10 to 20 EEFL lamps should be assembled which are composed of glass tubes, for example, having an outer diameter of 3 mm and a length of 300 to 500 mm. More specifically, in the manufacturing and assembling of this power supply unit, the both ends of a number of slender and fragile EEFL lamps must be inserted into capsule type sockets in the pair of power supply units, which are spaced with each other. Because of this reason, If the plurality of capsule type sockets are not arranged in the pair of power supply units with an accurate dimension and position, twist or distortion might occur in the plurality of EEFL lamps arranged in parallel. Thus, not only insufficient electrical contact is caused but also a mechanical stress is imposed on the slender and fragile EEFL lamps, which are possibly destroyed.
In general, in such back light units, there is a tendency that the length and numbers of EEFL lamps increase as a display scale becomes large and the resolution of a picture become high and thus there was a problem that a higher technique is required in manufacturing and assembling the power supply unit, resulting in the higher manufacturing cost.
The present invention provides a socket assembly, which is easily manufactured and assembled for the demand of small diameter, long size, and increasing number of EEFL lamps composing the flat panel type lighting device, and which is capable of stable lighting performance with a firm electric contact. It is another object of the present invention to provide a lighting device provided with such socket assembly.